Microlithography is used for the production of microstructured components such as for example integrated circuits or LCDs. The microlithography process is carried out in what is referred to as a projection exposure apparatus having an illumination system and a projection objective. The image of a mask (=reticle) illuminated via the illumination system is projected via the projection objective onto a substrate (for example a silicon wafer) which is coated with a light-sensitive layer (for example photoresist) and arranged in the image plane of the projection objective in order to transfer the mask structure onto the light-sensitive coating on the substrate.
In some instances, in the illumination system and also in the projection objective, a desired intensity distribution and/or an initially set polarization state can be altered in an unwanted fashion. The influences which are responsible for that include in particular birefringence effects which are variable in respect of time such as what is referred to as polarization-induced birefringence (PIB), compacting in non-crystalline material (for example quartz glass) of optical components, degradation phenomena and thermal effects as well as birefringence which is present in anti-reflecting or highly reflecting layers on the optical components as a consequence of form birefringence or by virtue of different Fresnel reflection and transmission for orthogonal polarization states.